In order to accurately diagnose disorders such as ulcers and cancer, physicians and veterinarians often need to obtain biological samples from hollow viscera like the gastrointestinal tract. Methods for obtaining such samples have traditionally involved very expensive and invasive techniques such as gastroscopy. Gastroscopy usually requires the patient to receive an endoscope through the nose or mouth, which then passes through the oesophagus and into the stomach. Once the endoscope tip is in the stomach, biopsy forceps may be inserted through the endoscope such that biopsy material can be taken from the gastric mucus and/or epithelial layer of the stomach. After biopsy, the endoscope is removed from the patient. Each of the steps involved in taking a biopsy may lead to serious patient discomfort, and consequently, gastroscopy is often performed under general anaesthesia or significant sedation. This potentially increases the problems associated with this procedure.
Accordingly, while gastroscopy has the benefit of allowing the operator to inspect the gastrointestinal mucosa, which would allow the detection of ulcerations and/or malignancies, such diseases are uncommon, especially in younger patients. Therefore, it would be preferable not to have to perform gastroscopy unnecessarily, and consequently, there is a requirement in the art for a procedure that is less invasive and more cost-effective, especially when it is necessary to study the normal or abnormal microbiological flora of the gut.
In recent times gastroscopic examination has, to a certain degree, been replaced with less expensive and less invasive techniques, such as digestible pharmaceutical capsules containing extractable strings. These extractable strings are often called gastric strings. To use, the patient holds the free end of the gastric string then swallows the capsule. The string plays out of the capsule as it travels through the patient's oesophagus until the capsule enters the patient's stomach. The capsule then either dissolves or passes through the patient's digestive system, leaving the string within the stomach. After a certain period of time the string is withdrawn, and the end of the string that was in the stomach is subsequently tested for the presence of various microorganisms or for gastrointestinal bleeding. Such a method and device is disclosed in U.S. Pat. No. 3,528,429 and Canadian Patent No 802,858, both of which are fully incorporated herein by reference.
U.S. Pat. No. 3,683,890 discloses a variation of the above device in which the outer dissolvable capsule encloses an inner capsule that is weighted with lead weight. The lead weight enables the string to drag against the inner lining of the stomach to enhance the sampling. The inner capsule is coated on the inside with silicon rubber, which collapses into a flexible bag upon disassociation of the outer capsule; the bag then passes through the pylorus of the stomach into the duodenum. When pulled from the patient, the string detaches from the bag, and the bag with the weight eventually passes with the patient's stool. Whilst this device has advantages over the system described above, the absorptive nature of the string used with this device is not great enough to collect a sufficient number of epithelial cells without dragging against the inner wall of the stomach. Moreover the device is relatively expensive to produce, because two capsules, a flexible bag and a lead weight are required.
Another prior art device has a steel ball that is non-detachably connected to a string. The steel ball promotes the dragging of the string against the inner lining of the stomach, which enhances sampling of epithelial cells. In use, the patient swallows the capsule. When the capsule enters the stomach, it either melts, dissolves or breaks apart and passes through the digestive system. After an indwelling period, the string is pulled out of the stomach, through the oesophagus and out of the mouth. Like other prior art devices, this system has advantages. However, when the string is pulled from the stomach, the steel ball often comes into contact with the gastroesophageal sphincter. This may cause discomfort to the patient, and in some cases, can damage it. This method and device is disclosed in U.S. Pat. No. 2,773,502, the entirety of which is incorporated herein by reference.
The prior art gastric strings described above have all been used for general gastrointestinal sampling, with varying degrees of success. One area for which gastric strings were hoped to be particularly useful was the detection of bacteria such as Helicobacter pylori(H. pylori). H. pylori has been shown to be associated with benign gastric and duodenal ulcers, as well as with gastric cancer, and this organism tends to live under the gastric mucus and between the epithelial cells of the stomach. These types of organisms are most often heavily concentrated in lower portions (i.e. the antrum) of the stomach, and therefore are particularly difficult to sample. Accordingly, the prior art gastric strings described above have had limited success in sampling for these organisms.
While other diagnostic methods are available to detect the presence of bacteria like H. pylori, these are known to be non-conclusive. Moreover, since these methods do not actually recover a sample of the bacterium in the stomach, it is possible not only that the organisms being specifically sought will not be present, but that other organisms that these tests can detect will be present. Accordingly, the physician often prefers to culture the organism before prescribing antibiotic therapy.
Thus, as can be seen, there is a real requirement for an inexpensive, non-invasive diagnostic procedure that allows for the recovery of significant samples from under the gastric mucus and between the epithelial cells of the stomach, and which would be particularly useful for sampling organisms such as H. pylori. 
One device that has recently been proposed for this purpose is disclosed in U.S. Pat. No. 5,738,110. This device includes a gelatin pharmaceutical capsule that contains a sampling string made of a mixture of bees' wax and mineral oil. The applicant of this patent contends that the sampling string used is sufficiently different to those used previously to overcome the problems highlighted above. However, one major problem that this device does not solve is the problem of bacterial contamination of the sampling string on removal from the gastrointestinal tract.
In all of the prior art devices described above, the gastric string passes through the mouth and oesophagus on withdrawal. However, none of these devices protects the gastric string from contamination upon its withdrawal from the stomach. This is a potential problem, as the mouth and oesophagus usually have a high background level of commensal flora, which can cause significant contamination of the string. This problem is especially relevant when trying to detect H. pylori, which is a very fastidious organism that is slow to culture. Consequently, the commensal organisms which contaminate the string often outgrow the H. pylori in culture to such a degree that detection of H. pylori is difficult if not impossible.
Thus, based upon the foregoing, it would be readily apparent to those of skill in the art that there is a need for a relatively inexpensive gastrointestinal sampling device that enhances sampling without contributing to the discomfort of the patient. Moreover, there is a requirement for a device that is capable of sampling microorganisms from specific regions of the gastrointestinal tract without becoming contaminated with microorganisms from other regions. Accordingly, the present invention attempts to overcome or at least alleviate some of the problems highlighted above, especially those related to the contamination problems discussed.